There is growing demand for very compact, low-cost, high frequency (i.e., microwave or millimeter wave) communications circuits.
In response to this demand, such circuits frequently employ mixed-technology silicon integrated circuit (IC) and gallium arsenide (GaAs) monolithic microwave integrated circuit devices (MMICs) supported on multi-chip module (MCM) substrate structures. The IC and MMICs usually consist of active devices and integrated passive components.
Since these products operate at high frequencies continuity of the RF ground plane is required for the MCM substrate and its mounted microwave GaAs and high-speed silicon active devices. Moreover, the efficiency of the interconnects in transmitting the signal power is required to be high to achieve a very low insertion loss and return loss
To address these requirements, a ball grid array structure (BGA) has been proposed, which allows feed-throughs at microwave and millimeter wave frequencies from electrical components, integrated circuits or MCM substrates to other circuitry such as circuit boards. See, e.g., U.S. Pat. No. 5,694,300 to Mattei et al., U.S. Pat. No. 5,717,245 to Pedder et al. and U.S. Pat. No. 5,355,283 to Marrs et al.
Ball grid arrays, however, conventionally utilize metal interconnects which are limited in their high frequency performance due to parasitic inductance, capacitance and resistance effects.